This invention relates to patterns used in mold flasks to mold sand for casting a standard AAR coupler yoke for a railway vehicle wherein cope and drag pattern parts are constructed to form an oblique relationship between the horizontal yoke pattern center plane and the pattern plates defining the parting line between cope and drag flasks.
As is well known in the art, railway vehicles are connected together by couplers that are supported by, inter alia, coupler yokes carried on the railway vehicles. A coupler yoke is a casting having a pocket to receive and maintain a draft gear assembly in operative contact with the coupler so that the forces applied to the coupler head are dampened by the gear. In freight car draft arrangements, a rectangularly-shaped block of metal is interposed between the butt end of the coupler shank and the front working end of the draft gear. This rectangularly-shaped metal block, usually referred to as a front follower, extends crosswise through the front end of the yoke draft gear pocket. The draft gear is compressible and moves in the draft gear pocket through a distance of travel afforded by the design of the draft gear and sill stops. Side walls at the front end of the coupler yoke form a coupler pocket to receive the butt end of the coupler shank. The yoke at its front end is joined to the shank of a coupler by a horizontal connecting cross-key in an E-type coupler, or by a vertical pin in an E/F-type coupler and an F-type coupler. Except for heat treatment, gaging and rough grinding, the coupler yoke casting is used, as cast, to transmit pull and buff forces to the draft gear in train service.
Standard AAR E-type coupler yokes and F-type coupler yokes are unitary castings each embodying a somewhat similar design of top and bottom straps extending rearwardly to an interconnecting rear end portion having lightener holes at its opposite faces and a rear draft seat at right angles to the top and bottom straps. From the rear end portion, the top and bottom straps have a substantially uniform width along the major portion of their length to a point where an enlargement to their width forms a short transition zone extending to the front end portion of the coupler yoke. In an E-type coupler yoke, a key slot is formed in the head end side walls extending between the top and bottom strap portions and forwardly to a nose or jaw. The nose has outwardly-diverging side walls to accommodate lateral movement of the coupler shank. The side walls of the front end portion are also formed with front block follower seats which face toward the rear draft gear seat. In an F-type coupler yoke, the front end portion forwardly of the front follower seats has a bored pinhole in the top and bottom walls extending forwardly from the top and bottom straps. Walls usually called "head end side straps" interconnect the walls containing the bored connecting pinhole and form a coupler pocket to receive a butt part of an E/F-type or an F-type coupler shank.
Conventionally, cores are used in the cavity of a sand mold to produce a coupler yoke casting. Cope and drag patterns for a standard coupler yoke usually require the use of 11 separate core members produced from seven different designs of core boxes. The multiplicity of cores is undesirable because it requires an excessive amount of facilities, labor and finishing operations for the resulting casting. For example, a matching set of cope and drag cores as set in drag flask molds, require grinding to provide the required height and assure flat mating surfaces. Cope and drag cores were also pasted and banded together for use in the drag molds of the flasks. Other core finishing operations include repairs to overcome surface defects. All the cores are manually set in the drag mold and anchored at the desired position. After the cope and drag flasks are joined together with the cores in place, movement to the pouring floor sometimes produced unwanted shifting of the cores and/or flasks which cannot be detected until after the casting is removed from the mold. Excessive hand grinding operations are required because of the multiplicity of the cores. More recently, coupler yoke castings are produced by the use of a single head end core in the cope and drag flasks of a mold. However, an excessive number of defective yoke castings still occur because of defects caused by misaligned core and mold surfaces of the casting.
The present invention is addressed to a novel pattern assembly to mold sand in the cope and drag flasks of a mold in a manner to facilitate the use of a single core. In the past, when a single core was used throughout a mold, the cope-to-drag parting line was chosen to correspond to one longitudinal center plane of the coupler yoke casting. The cavities in the cope and drag molds formed, with the core member, equal halves of the yoke casting. The parting line extended the full length of the strap sections inside and outside thereof midway of the strap mold height. Yoke castings are usually molded on their sides, i.e., reorientated at an angle of 90.degree. from their usual operative position.
The parting line defined by the cope and drag has also been arranged to extend about one inch from the side edge of the straps. In this way, the patterns are designed so that the drag portion includes about four inches of the molded strap height and the cope portion includes the remaining part of the straps which is about one inch. The parting line of the patterns and the molds applies to the internal parts of the casting as well as the external wall surfaces. The pattern parts are mounted on perfectly flat plates or boards with the face surfaces defining the parting line. The selection of the parting line for a coupler yoke casting was in the past characteristically chosen because of the overwhelming symmetrical design about longitudinal center planes of the castings. This invention is addressed to the novel concept for providing yoke mold patterns for mounting upon pattern plates that define a parting line between cope and drag molds that eliminate disadvantages arising out of traditional selection of a parting line that required yoke draft gear pocket cores and producing a casting requiring excessive finishing operations, particularly at critical areas requiring relatively smooth surfaces without fins or ribs and of close dimensional tolerances.